King F G, Manson H J, Snellen J W, Chang K S
Can Anaesth Soc J. 1984 Jul;31(4):460-5. doi: 10.1007/BF03015426.
We have investigated sensible respiratory loss, which is usually taken as the product of expired volume and the temperature difference between inspired and expired air (VE X delta T). Air temperature was measured with a 0.122 mm copper-constantan thermocouple mounted in the mouthpiece of a T-piece breathing system, and expired volume with a pneumotachograph. Changing air temperature (delta T) at the mouth and expired air volume (VE) were recorded simultaneously while the subject voluntarily breathed at different tidal volumes and rates. Inspired temperatures were controlled at 12.05 degrees C, 21.80 degrees C and 25.74 degrees C at a low dewpoint temperature of 4-5 degrees C. Temperature volume "loops" were constructed using an x-y plotter. The areas of each "loop" and enclosing rectangle (VE X delta T) were measured. The difference was divided by the weight of the rectangle to give the percentage of overestimation of sensible heat loss, which ranged from 5.5 to 17.2 per cent. The error increased significantly with decreasing tidal volume and increasing respiratory rate.
我们研究了显热呼吸损失，通常将其视为呼出气体量与吸入和呼出空气温差的乘积（VE×ΔT）。空气温度用安装在T形管呼吸系统接口处的0.122毫米铜-康铜热电偶测量，呼出气体量用呼吸速度描记器测量。当受试者以不同潮气量和呼吸频率自主呼吸时，同时记录口腔处的空气温度变化（ΔT）和呼出气体量（VE）。在露点温度为4-5摄氏度的低温条件下，将吸入温度控制在12.05摄氏度、21.80摄氏度和25.74摄氏度。使用X-Y绘图仪绘制温度-体积“环路”。测量每个“环路”和包围矩形（VE×ΔT）的面积。将差值除以矩形的重量，得出显热损失高估的百分比，范围为5.5%至17.2%。误差随着潮气量减小和呼吸频率增加而显著增大。
